Would you be able to have him/her walk on something straight like a ruler so the tail is straight out? That would make it easier to tell as I would just be guessing right now.
I would concur with the others, I think it's a female. The base of her tail is very narrow, and her colors are very female (no white lateral line, the peachiness, the peach throat area, etc.). She doesn't look super tiny either, she has a good size to her, so I think if she were male he'd be big enough to be obvious by now.